1. Field of the Invention
The invention relates to an apparatus and method for treating a fibrous suspension and, more particularly, to a deaeration apparatus, cleaning apparatus or pressurized screen for treating a fibrous suspension.
2. Discussion of Background Information
As is known, fibrous paper stock required for paper production is treated on a paper machine in a stock preparation. With a majority of the process steps carried out in this part of the installation of a paper mill, the fibers are treated and processed in suspension, in particular an aqueous suspension, with a fiber content between 0.5 and 8%. The major part of these process steps is carried out in closed apparatuses, i.e., those that are part of a closed system.
Apparatuses which can be used for the stock preparation can, e.g., be pressurized screens. In these types of apparatus, the fibrous suspension to be treated is pumped through a wet wire, e.g., a screen cylinder (also referred to as a screen basket), by an applied pressure difference. In this way, a part of the fibrous suspension is rejected at the openings of the screen and removed from the housing through a separate opening. A rotor is moved past the screen to prevent the screen from becoming clogged by fibers or rejected contaminants.
Apparatuses can also be designed to deaerate or degas the fibrous suspension. To accomplish such deaerating or degassing, the suspension is put into rapid rotation by the rotor, which causes gases, e.g., air, to accumulate in the center as a result of centrifugal forces. The gases are then removed through a suitable opening. Apparatuses of this type are suitable for replacing complex vacuum-operated degassing containers. They can be arranged directly before a pressure-increasing stock pump which conveys the suspension to the next treatment step. Naturally, the operating energy input used to drive the rotor is a cost factor in the operation of such an apparatus.